Simple and ultra sensitive sequence-specific DNA biosensors are needed for the rapid diagnostic of infections and genetic diseases, as well as for environmental and forensic applications.1 For this purpose, various optical and electrochemical DNA sensors have been proposed.2-8 However, most of these proposed DNA sensors rely on some form of chemical amplification, such as PCR,9 which in turn can require the use of complex mixtures and sophisticated hardware to perform the necessary enzymatic reactions.
More recently, rapid fluorescence-based DNA detection methods based on water-soluble conjugated cationic polymers have been described.10-14, 23-26 Here, a polycationic polymer is used as a light-harvesting multichromophore (see, for example, United States Patent Application Publication No. US 2004/0219556 A1 (Nov. 4, 2004) (Bazan et al.)). A sensor based on a neutral peptide nucleic acid (PNA) and having a signaling chromophore having a base sequence complementary to a target polynucleotide of interest is provided. Upon contacting the target polynucleotide in a sample, the polycationic multichromophore is brought into proximity with the signaling chromophore by virtue of electrostatic interactions with the target polynucleotide. Excitation of the multichromophore then produces light emission from the signaling chromophore. While this method provides for a quick and reliable way to measure the quantity of polynucleotides in a sample, it does not by itself allow for the detection of very minute quantities of nucleotides in the sample.
There thus remains a need for a method allowing for the rapid and highly-sensitive detection of polynucleotides in a sample without resorting to nucleotide amplification techniques, such as PCR. Moreover, there remains a need for compositions and articles of manufacture useful in such a method.
The present invention seeks to meet these and other needs.